User Guide

HE910 Hardware User Guide
1vv0300925 Rev.18 – 15-06-2012
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 36 of 91
HE910
Mode
Average
(mA)
Mode description
SWITCHED OFF
Module supplied but Switched Off
Switched Off
40uA
IDLE mode (WCDMA)
AT+CFUN=5
1.2
Disabled TX and RX; DRX7
IDLE mode (GSM/EDGE)
AT+CFUN=1
19
Normal mode: full functionality of the module
AT+CFUN=4
16.5
Disabled TX and RX; module is not registered on the network
AT+CFUN=5
0.8
Disabled TX and RX; DRX9 (1.1mA in case of DRX5)
Operative mode (WCDMA)
WCDMA Voice
152
WCDMA voice call (TX = 10dBm)
WCDMA HSDPA (0dBm)
187
WCDMA data call (Cat 14, TX = 0dBm)
WCDMA HSDPA (22dBm)
494
WCDMA data call (Cat 14, TX = 22dBm)
Operative mode (EDGE)
EDGE 4TX+2RX
EDGE Sending data mode
GSM900 PL5
495
DCS1800 PL0
484
Operative mode (GSM)
CSD TX and RX mode
GSM VOICE CALL
GSM900 CSD PL5
220
DCS1800 CSD PL0
167
GPRS 4TX+2RX
GPRS Sending data mode
GSM900 PL5
580
DCS1800 PL0
438
The GSM system is made in a way that the RF transmission is not continuous, else it is packed
into bursts at a base frequency of about 216 Hz, and the relative current peaks can be as high as
about 2A. Therefore the power supply has to be designed in order to withstand with these
current peaks without big voltage drops; this means that both the electrical design and the board
layout must be designed for this current flow. If the layout of the PCB is not well designed a
strong noise floor is generated on the ground and the supply; this will reflect on all the audio
paths producing an audible annoying noise at 216 Hz; if the voltage drop during the peak current
absorption is too much, then the device may even shutdown as a consequence of the supply
voltage drop.
NOTE:
The electrical design for the Power supply should be made ensuring it will be capable of a peak
current output of at least 2 A.